# A force of 25 N acts upon a 5 kg block. Calculate the ```Solving Physical Science Word
Problems:
• Write down all given information
• Write the formula you need to solve the
problem.
• Substitute the numbers in the equation.
• Show all operations and solve.
• Answers should include both numbers and
units.
Brandon
pushes a 400
kg rock until it
accelerates at
the rate of 8
m/s2.
What is the
force required
to produce
this
acceleration?
• M = 400 kg
• A = 8 m/s/s
• F=M∙A
• F = 400 kg ∙ 8 m/s/s
• F = 3200 N
Riley exerts a force • F→ = 150 N
of 150 N on a 50
• M = 50 kg
kg box. The box
• If the box does not move,
doesn’t move.
F← = 150 N
How much force
does the box exert
on Riley?
A force of 25 N acts upon a 5 kg
block. Calculate the acceleration.
• F = 25N = 25 kg ∙m/s/s
• M = 5 kg
• A=F&divide;M
• A = 25 &divide; 5
• A = 5 m/s/s
An object of
mass 45 kg is in
free fall in a
vacuum where
there is no air
resistance.
Determine the
acceleration of
the object.
• No air resistance means
the object is in “free fall”.
• Free fall means the only
force acting on the object
is the force of gravity (its
weight).
• The acceleration due to
gravity is 9.8 m/s/s.
Calculate the acceleration if. . .
• Kiana pulls a
6 kg block
pulled
across a
table with a
force of 40
Newtons. A
frictional
force of 4 N
opposes the
motion.
• F = 40 N →
• F=4N←
• Net Force = 40 N – 4 N = 36 N
•
•
•
•
M = 6 kg
A=F&divide;M
A = 36 N &divide; 6 kg
A = 6 m/s/s
Tyler has a mass of • M = 65kg
65kg. What is
• g = 9.8 m/s/s
Tyler’s weight in
Newtons?
• Weight = m ∙ g
In pounds?
• Weight = 65 ∙ 9.8
• Weight = 637 N
• 1 lb. = 4.4N
• Weight = 637 /4.4
• Weight = 144.7 LBS.
Now it’s your
turn!!!!
What is the force
required for
Marcus to throw a
15 kg ball up into
the air at 3 m/s/s?
• Marcus would first have to
overcome the force of
gravity on the ball…
• Force of gravity on the
ball= m ∙ g = 15 ∙ 9.8 m/s/s
• F ↓ = 147 N
• F ↑ = m ∙ a = 15kg ∙ 3m/s/s
• F ↑ = 45 N
• Total F needed to throw
ball into the air = F↑ + F↓
= 45N + 147 N = 192N
Josh, who has a
mass of 80 kg, is
extremely clumsy
and fell out of an
airplane during
training. OH NO!!!
He reaches
terminal velocity
before he can be
rescued. What is
the force of the air
resistance?
• Acceleration due to gravity
= 9.8 m/s/s
• M = 80 kg
• Force of gravity = F↓
• F↓ = M ∙ g = 80 ∙ 9.8
• F↓ = 784 N
• Air Resistance = F↑
• Terminal Velocity occurs
when force of gravity = air
resistance (F↑ = F↓)
• F↑ = 784 N
An object with a
mass of 30 kg is
falling in air and
experiences a
force due to air
resistance of 50
newtons.
A = F &divide; M,
But first you have
to calculate the
net force.
•
•
•
•
•
•
M = 30 kg
F↑ (air resistance) = 50 N
F ↓ = weight
Weight = m ∙ g
Weight = 30 kg ∙ 9.8 m/s/s
Weight = 294 N
• Net Force = Weight – Air Resistance
• Net Force = F ↓ - F↑
• Net Force = 294 N – 50 N
• Net Force = 244 N
An object with a
mass of 30 kg is
falling in air and
experiences a
force due to air
resistance of 50
Newtons.
• A=F&divide;M
• A = 244 N &divide; 30 kg
• A = 8.13 m/s/s
A 40 kg cannon
is pushed with a
force of 200 N.
What is its
acceleration? If
you put a 40 kg
cannonball into
the cannon and
push it with the
same force, how
much does it
accelerate?
•
•
•
•
M = 40 kg
F→ = 200N
A = F &divide; M = 200 &divide; 40
A = 5 m/s/s
•
•
•
•
M = 40kg + 40Kg = 80kg
F→ = 200N
A = F &divide; M = 200 &divide; 80
A = 2.5 m/s/s
Now it’s your
turn!!!!
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